I suspect that the extra heat is caused by the injectors drawing more current[still within the the fuse limit]. Internal failure[coil gets damaged . Bad chinese crap knockoffs. If both sets act similar thay might come from the same source. Check the fuse rating and likely measure injectors resistance, and amps used while running.
Every connector for each sensor has already been replaced due to being brittle from heat/climate. What I haven't replaced are the connectors for the injectors (just ordered them) and to check the plugs at the ECM to make sure those connectors are all good (using the .030 drill bit method...I just need to get a 030 drill bit). I'm also looking at running new power and ground wires from ECM to the injectors just to eliminate any possible breaks in the wires.
Good old thermal run away...high resistance causes heat, heat causes resistance to increase, repeat cycle until smoke leaks out of wires.
Well I thought I had found my issue... I was changing out the connectors for the injectors and found this when I stripped back the wiring. Funny thing is this is 1 wire for each injector, so it wasn't like a sloppy connector replacement job. Alas, cleaning this all up did not resolve the issue.
legit_wiring.jpg
I then spent a good hour pulling each pin from the ECU connector and squeezing each so that I ensured I had good connections.
Neither fixed the issue.
About the only thing I haven't replaced lately is the pickup in the distributor. I do have a brand new one that was never installed because when I went to install it I found the bushings in the old dizzy were shot so I just replaced the whole thing. So I'll throw that in tomorrow.
And because I'm a glutton for punishment, I just bought a 7427 to do that swap.
There were so many cases of wires getting caught in the air cleaner and being pinched that GM actually issued a bulletin instructing technicians to twist the two connectors together several times to reduce slack. But whoever added those wires really missed the mark. TBI injector wires use a special insulation which is gasoline resistant. Gasoline can wick up the wires and soften PVC insulation. In most cases the wires are not spliced. Each wire is one continuous run from ECM to injector. That splice... any spark with fuel in the wire and oxygen nearby could result in a fire. At the bare minimum using the correct insulation and using a crimp / solder splice should be considered top priority.Well I thought I had found my issue... I was changing out the connectors for the injectors and found this when I stripped back the wiring. Funny thing is this is 1 wire for each injector, so it wasn't like a sloppy connector replacement job.
Where do you get a vacuum source for your accessories from?
I just noticed from your photo you'd blocked off a couple of ports on the front of the TBI unit.
I assume the larger hose from the manifold goes to the brake booster and the two other from your TBI unit are for the PCV and canister purge?
There is a port in the intake behind the TBI unit for the accessories. Right now I have it blocked off to eliminate any potential vacuum leaks in the climate control system. On the front the 2 that are hooked up go to the canister and the PCV. The truck has hydroboost brakes so no vacuum booster.Originally Posted by Kitch
Luckily both of those were outside of the TBI. The new connectors for the injectors had long enough leads that I was able to eliminate those patch pieces. Soldered and shrink tube.
UPDATE...
So after redoing all of the grounds, new O2, inspecting the entire harness for issues I still had that 1400-1600rpm lean spike that I just could not get rid of. So late one night I googled the symptom and it led me back to a thread here where someone had a similar issue and worked it through the Injector Bias setting (http://www.gearhead-efi.com/Fuel-Inj...rottle-low-rpm). This basically accounts for slow opening injectors - it adds time to the pulse to account for slow opening. It is recommended to increase this value when fuel pressure is increased. Hmmm...this problem really showed up after I installed the remote fuel regulator and set my pressure to 13 (factory regulator was giving me 10-ish).
OK, so went in and doubled the value and wow smooth throttle transition with no lean spike. Drove it around a lot to make sure. But as the author of that other thread found, this caused the system to drop in and out of async any time I was at light throttle no matter what the RPM. That makes for a really unpleasant driving experience. Also noticed that my INT/BLM numbers were showing that my VE was way off with the new pulse setting.
So, I went back to the drawing board. Started back with a totally factory AZFW (7.4, manual, 4.10 gear) tune. I had been wanting to increase fuel pressure for a while for various reasons, so I calculated a new BPW based on my new fuel pressure, added about 50% to the injector bias and went for a drive. Lean spot at 1400 was back, but was actually driveable, and got in/out of async any time vacuum was >20-ish. Did some light throttle driving and data logging and tweaked the VE, then did it again and tweaked some more. Definitely got better with the async issue. Still have the lean spike. Funny I can see the BLM showing 150+ right then, but when I play back the logs and look at the history settings (last, average, highest, etc...) all of the cells in that area are showing right around 126-130.
As of now I think I am comfortable that I don't have any hardware related issues and this is all related to the tune.
Question - how do I see BLM and INT values on the dashboard in TunerPro, but when I review the logs and the history tables I can't see those values?
So I think async is tripping now due to long injector cycles and it is trying to lean it out. Problem is when async kicks in it feels like fuel totally cuts off and I get a momentary deceleration followed by async turning off and engine picks back up again.
As I seem to have eliminated wiring/sensors/hardware as the issue, and I need way better logging to be able to see what is really happening, I'm thinking a 7427 swap might be a good thing. I have the ECU, the Moates adapter for the chips, and a good starting BIN.
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